GettingStarted.md

id	title
getting-started	Getting Started

The problem

You want to write maintainable tests for your React Native components. As a part of this goal, you want your tests to avoid including implementation details of your components and rather focus on making your tests give you the confidence for which they are intended. As part of this, you want your testbase to be maintainable in the long run so refactors of your components (changes to implementation but not functionality) don't break your tests and slow you and your team down.

This solution

The React Native Testing Library (RNTL) is a lightweight solution for testing React Native components. It provides light utility functions on top of react-test-renderer, in a way that encourages better testing practices. Its primary guiding principle is:

The more your tests resemble the way your software is used, the more confidence they can give you.

This project is inspired by React Testing Library. Tested to work with Jest, but it should work with other test runners as well.

You can find the source of QuestionsBoard component and this example here.

Installation

Open a Terminal in your project's folder and run:

Using yarn

yarn add --dev @testing-library/react-native

Using npm

npm install --save-dev @testing-library/react-native

This library has a peerDependencies listing for react-test-renderer and, of course, react. Make sure to install them too!

:::info In order to properly use helpers for async tests (findBy queries and waitFor) you need at least React >=16.9.0 (featuring async act) or React Native >=0.61 (which comes with React >=16.9.0). :::

Additional Jest matchers

In order to use addtional React Native-specific jest matchers from @testing-library/jest-native package add it to your project:

Using yarn

yarn add --dev @testing-library/jest-native

Using npm

npm install --save-dev @testing-library/jest-native

Then automatically add it to your jest tests by using setupFilesAfterEnv option in your Jest configuration (it's usually located either in package.json under "jest" key or in a jest.config.js file):

{
  "preset": "react-native",
  "setupFilesAfterEnv": ["@testing-library/jest-native/extend-expect"]
}

Flow

Note for Flow users – you'll also need to install typings for react-test-renderer:

flow-typed install react-test-renderer

Example

import { render, fireEvent } from '@testing-library/react-native';
import { QuestionsBoard } from '../QuestionsBoard';

test('form submits two answers', () => {
  const allQuestions = ['q1', 'q2'];
  const mockFn = jest.fn();

  const { getAllByA11yLabel, getByText } = render(
    <QuestionsBoard questions={allQuestions} onSubmit={mockFn} />
  );

  const answerInputs = getAllByA11yLabel('answer input');

  fireEvent.changeText(answerInputs[0], 'a1');
  fireEvent.changeText(answerInputs[1], 'a2');
  fireEvent.press(getByText('Submit'));

  expect(mockFn).toBeCalledWith({
    '1': { q: 'q1', a: 'a1' },
    '2': { q: 'q2', a: 'a2' },
  });
});

You can find the source of QuestionsBoard component and this example here.